This invention relates to thermodynamic condensate traps, and particularly, although not exclusively, to steam traps.
A thermodynamic condensate trap comprises a trap body and a cap which define a trap chamber. A valve element is displaceable within the trap chamber between limit positions defined by a stop face on the cap and a seating face on the trap body. The trap body has inlet and outlet passages which emerge at the seating face; whereby seating of the valve element on the seating face under pressure maintained in the trap chamber isolates the inlet and outlet passages from each other thereby to close the trap.
In such a condensate trap, when used as a steam trap, the trap is kept closed by pressure generated by flash steam within the trap chamber. As the trap cools, the steam condenses and the pressure in the trap chamber falls to a level at which the valve element can be displaced away from the seating face by fluid under pressure in the inlet passage. Condensate can then flow through the trap by passing from the inlet passage to the outlet passage. Initially, the discharged condensate is relatively cold, but it becomes progressively hotter and eventually reaches a temperature at which it will re-evaporate within the trap chamber. This causes the trap to close again, and the cycle is repeated. If there is rapid heat loss from the trap chamber to the ambient surroundings, the cycle time is short, resulting in premature wear of the steam trap components.
In some circumstances it is desirable to control the loss of heat from thermodynamic condensate traps. In order to achieve this control, it has been proposed to fit a cover over the condensate trap to reduce heat loss. However, such covers represent an extra component which needs to be stocked, and they are also subject to unauthorized removal, in which case their thermally insulating properties are lost. U.S. Pat. Nos. 3,664,363 and 4,736,886 and Japanese Published Patent Specification No. 12497/71 disclose thermodynamic steam traps with additional covers.
According to the present invention there is provided a thermodynamic condensate trap comprising:
a trap body having a seating face; PA1 a cap fitted to the trap body and having a stop face, the trap body and the cap defining a trap chamber; PA1 a valve element which is displaceable within the trap chamber between limit positions defined by the stop face and the seating face; and PA1 inlet and outlet passages provided in the trap body and emerging at the seating face, whereby seating of the valve element on the seating face under pressure maintained in the trap chamber isolates the inlet and outlet passages from each other thereby to close the trap, PA1 wherein the cap has thermal insulating means for reducing heat transfer between the trap chamber and the ambient surroundings.
The provision of thermal insulating means in the cap, in accordance with the present invention, slows down the exchange of heat and increases the cycle time of the trap operation. This increases the useful life of the trap.
Because the thermal insulation is afforded by the cap itself, no additional components are required, and unauthorized removal cannot occur.
In a preferred embodiment of a condensate trap in accordance with the present invention, the cap has a top portion, the internal side of which has the stop face, and a skirt which defines a side wall of the trap chamber.
The thermal insulating means may be provided in either or both of the top portion and the skirt. The thermal insulating means may take the form of an air space. Thus, the thermal insulating means in the top portion may be provided by an annular recess in the outside surface of the top portion of the cap, which may be closed by a cover plate. The air space in the skirt may take the form of a circumferential recess extending around the skirt, which recess may be open at the lower region of the skirt. Where air spaces are provided in both the top portion and the skirt, these air spaces may come into close proximity with each other in the region of the outer circumference of the air space in the top portion. Thus, the air space in the skirt may extend for substantially the full height of the skirt.